The use and importance of the Internet as a means of exchanging information over recent years has increased dramatically. Various businesses are now using the Internet to advertise their products and services. The operation of the Internet and the use of html is well understood within the art and therefore only brief details thereof will be presented here. Further information relating to the Internet and HTML can be found in, for example, "HTML Sourcebook, A complete guide to HTML", by Graham, I. S. (John Wiley and Sons, Inc), "Spinning the web" by Andrew Ford (International Thomson Publishing, London 1995) and "The World Wide web Unleashed" by John December and Neil Randall (SAMS Publishing, Indianapolis 1994). Information accessed via the Internet is typically displayed using a web Browser. The web Browser can interpret the HTML contained within an HTML document or web page. The HTML controls the presentation of output to a visual display unit of the computer running the web Browser as is well known within the art. A web page typically contains so-called hyperlinks to other web pages. Each hyperlink is a Uniform Resource Locator (URL) which is used to access further a web page or HTML document stored on a particular server connected to the Internet. In order to display the other web pages, the user selects the URL corresponding to that web page using a mouse. The associated web page or HTML document is retrieved and forwarded to the user's web Browser for subsequent display in the conventional manner. Selecting a URL from one web page causes the web page identified by that URL to be displayed in place of the currently displayed web page thereby removing the currently viewed web page from view.
A compound document is a document which comprises many component parts. Each component part typically contains and displays data of a particular type. For example, the text of a patent application may be contained within a text component of a document while the accompanying drawings are contained within graphics component of the document. The text and graphics components can manipulate their respective data independently of each other. Furthermore, the underlying code controlling the display or processing of the data associated therewith can be modifed or replaced independently of the other component parts constituting the document. Many environments exist for the development of compound documents. An example of such an environment is the OpenDoc environment available from Component Integration Laboratories (Sunnyvale, Calif., U.S.A.), and described in "The Byte Guide to OpenDoc" by Andrew McBride and Joshua Susser, Osborne/McGraw-Hill, Berkeley Ca, 1996, ISBN 0-07-882118-5. Further information relating to the structure of compound documents can be found in the above reference.
The HTML documents or web pages as described above can be utilised to produce single layer documents which comprise different data types. For example, the &lt;IMG SRC="filename.gif"&gt; tag can be used to include an image within a rendered HTML document. The image contained in the file "filename.gi" is included by the web browser in the rendered HTML page. The current documents accessible on the Internet can only be viewed as single layer documents comprising text and images. The images within a rendered HTML documents are rendered by the web Browser. HTML does not support nested or multi-layered HTML documents.